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Homework Help: Have I lost my crystals?

  1. Oct 2, 2008 #1
    In organic lab this week we were mixing (1-R, 2-S) ephedrine with mandelic acid to get crystals. I dissolved both compounds in 6 mL 95% EtOH and then poured them together. After cooling + glass prodding I should have had no trouble getting crystals. HOWEVER, during the cooling I accidently added about 10 mL of methylene chloride to the mixture, and was unable to get crystals at room temp. I knew DCM has a low boiling point so I just boiled off all of the solvent and added 12 mL of EtOH 95%. I then re-heated the soln and let it cool. I prodded the sides with a glass rod and still nothing. Then I decided to put the soln (it was in a 100 ml erlenmeyer) on ice. Before you know it I had crystals. Can I be confident that these are the crystals of the resulting compound when ephedrine and mandelic acid are reacted?

    Once I got crystals I stored them in my drawer for next week at room temp. It seems nobody else needed ice, so i'm worried that everything will be redissolved when I get back.

  2. jcsd
  3. Oct 2, 2008 #2


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    A lot of things can happen with boiling , I would take some melting point data of the sample.
  4. Oct 6, 2008 #3


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    You want to carefully cool the sample... not shock it with ice. If you are unsure about your procedure, just remove a few crystals of what you have and reheat the whole thing. Once it has slowly come to room temperature, add the crystals and pray to whatever deity you worship.

    Good luck.
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